This invention relates to battery electrolytes and more particularly to solid polymeric electrolytes.
Solid electrolytes have been shown to be a practical substitute for aqueous electrolytes in electrochemical cells or batteries wherein the electrolytes have been Ag.sub.3 SI, one of the family MAg.sub.4 I.sub.5 (M=K, Rb, Cs), or one of the beta-aluminas, M.sub.2 O.11Al.sub.2 O.sub.3 (M=Li, Na, K, NH.sub.4, Tl, Ag, etc.). Polymers offer the potential of being used as solid electrolytes because of their ability to be formed into thin films and the ability of some polymers to dissolve salts and transport ions. Polymers electrolytes offer the advantage of being readily prepared in thin films of large area both of which reduce cell resistance and allow large current drains at low current densities.
The desirable properties for solid polymeric electrolyte includes both high ionic conductivity and good mechanical strength. Attempts to increase ionic conductivity by lowering the molecular weight or the glass transition temperature result in specimens that are too fluid or mechanically weak films. Crosslinking can lead to stronger films, but the conductivity drops. The largest research effort has been on single phase high polymers with capability to dissolve salts and to form polymer-salt complexes. However, the conductivity of these polymer systems is only at the order of 1.times.10.sup.-6 S/cm at room temperature.